CLEVELAND – LeBron James issued his first guarantee as a pro last night. Then King James laid an egg.

The slumping Cavaliers are no longer a lock for the playoffs, as they were stunned by the moribund Knicks last night, 95-89, at Gund Arena, with James committing the key turnover in the final minute to seal their loss.

James, the spectacular second-year swingman being compared to Michael Jordan, said before the game to count on Cleveland in the postseason.

“We ain’t worried about not making it,” James said. “We’re going to make it.”

Don’t be so sure. Amidst a potential colossal collapse, the seventh-place Cavs lead the ninth-place Nets now by just two games and the Sixers by one and play in Washington and Detroit on the road in its next two games.

Trailing 72-70 in the fourth, the Knicks showed rare fourth-quarter magic, as Herb Williams benched Stephon Marbury for the period, allowing Jamal Crawford and Jermaine Jackson to run the backcourt. Crawford led the Knicks to victory, scoring 13 of his 26 in the fourth.

James had 25 points, a career-high 18 rebounds and seven assists but shot 7 of 25. And down four with 57 seconds left, James got confused at the perimeter, looked to shoot but then decided to pass inside, throwing the ball several feet over the head of Ira Newble, intercepted by Jerome Williams. Ballgame.

The Knicks played physically against James, showing him different defenders, from Malik Rose, to Jerome Williams to Tim Thomas.

The Knicks, without Marbury, went on a 13-0 run in the fourth, capped by a Crawford trey. Maurice Taylor also keyed the fourth-quarter surge, scoring 11 of his 16, mostly on midrange jumpers.

The Cavs are 6-8 under interim coach Brendan Malone, who replaced the axed Paul Silas March 21. James said yesterday he would like a say in the new coach.

“I would like to have a lot of input,” said James, who was voted among the “top 100 influential people” in the world by Time this week. “I’m the one whose going to be playing with him.”

The Knicks led 65-53 with 5:56 left in the third quarter when James led a 19-5 charge. A 3-pointer from the left wing by James got it to 67-62. Then Crawford coughed up the ball and James came back for a fastbreak dunk.

After driving ferociously to the basket, he got hacked, went to the line and made both free throws, putting the Cavs up 69-67. The fans were chanting MVP and all was right in the Cavs world. Now it’s caving.

Since the ownership change, James has expressed frustration, leading to speculation he will want a change of scenery when his contract runs out in 2007, or sooner. The turmoil has reached a point that GM Jim Paxson is reportedly going to be fired soon.

Two weeks ago, Knicks superfan Spike Lee, an acquaintance of James as fellow Nike promoters, fantasized about having him play for the Knicks, claiming he has a bump in his contract to play on Broadway.

When asked about Spike’s dreams, James said, “[Spike’s] a good dude. I know that. [But] I don’t want to get into that. I’m worried about putting on the Cavalier uniform every night.”